Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/30—Inkjet printing inks
  • C09D11/32—Inkjet printing inks characterised by colouring agents
  • C09D11/324—Inkjet printing inks characterised by colouring agents containing carbon black
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/0023—Digital printing methods characterised by the inks used

Definitions

• the present invention relates an inkjet recording ink, and also relates to an ink cartridge, image forming method, and image recorded matter using the inkjet recording ink.
• the inkjet recording has been known as an advantageous system as it can easily attain full-colored images with a simpler process than that of other recording systems, and also attains images of high resolutions by apparatus of simple configuration.
• dye inks in which various water-soluble dyes are dissolved in water or a mixed solution of water and an inorganic solvent are used as inkjet recording inks. These dye inks have excellent clear color tone, but has poor light resistance.
• pigment inks in which a carbon black or various organic pigments are disposed have excellent light resistance, and thus researches have been actively conducted on such pigment inks.
• pigments are insoluble to water unlike dyes, it is important to stably disperse the pigment in water in the state of fine particles.
• dispersion state is not necessary easy to achieve.
• absorption equilibrium of a dispersant and the pigment is disturbed, affecting the interaction between the pigment particles.
• the ink may cause the physical change and/or a large amount of the aggregated matter may be generated during the storage of a long period.
• the physical change, especially a change in its viscosity, and/or generation of aggregated matters can be crucial to an ink for use in an inkjet printer.
• any ink containing a polymer dispersant such as styrene-acryl copolymer or styrene-maleic acid copolymer (see Patent Literature 1), and a sodium naphthalenesulfonate-formalin condensate (see Patent Literature 2) or containing a surfactant, such as polyethylene glycol alkyl phenyl ether (see Patent Literature 3), polyethylene glycol alkyl phenyl ether sulfate (see Patent Literature 4), and polyethylene glycol alkyl phenyl ether phosphate (see Patent Literature 5), an average particle diameter of a pigment is large, and thus these inks have poor ejection stability or liquid stability.
• a polymer dispersant such as styrene-acryl copolymer or styrene-maleic acid copolymer (see Patent Literature 1), and a sodium naphthalenesulfonate-formalin condensate (see
• Patent Literature 6 discloses a method for removing aggregated matters that are generated during the storage for a long period in advance by heating a pigment ink at 50° C. for 100 hours to 500 hours.
• Patent Literature 7 realizes this treatment within a short period by heating a pigment, insoluble resin emulsion and saccharide at 65° C. to 80° C. for 0.5 hours to 3 hours.
• Patent Literature 8 discloses that an ink having a less viscosity change after storage for a long period can be provided by heating a pigment, water and polysaccharide in a solution having pH of 8 or more at 60° C. to 180° C.
• Patent Literature 9 discloses that an ink having a sharp particle size distribution, excellent glossiness and excellent color reproducibility can be provided by heating a colored fine particle dispersed ink containing a colorant and a resin at 35° C. or more.
• Patent Literature 10 discloses that an inkjet ink having excellent ejection stability, sufficient fixing ability and sufficient water resistance by defining an average particle diameter and glass transition temperature of a urethane resin.
• Patent Literature 11 discloses that an image fixing ability, ink storage stability, and ejection stability can be maintained at a desirable degree by selecting a certain polyurethane resin even when a particle diameter of a pigment is in the range of 70 nm to 180 nm.
• Patent Literature 12 discloses that a sufficient image fixing ability and ink storage ability can be attained by specifying a ratio of a urethane resin and a pigment, formulated amount thereof and a particle diameter of the pigment.
• Patent Literature 13 discloses that a sufficient image fixing ability can be attained by defining an acid value of a free acid of a urethane resin and a surface tension of an ink.
• Patent Literature 14 discloses that an image fixing ability, ink storage stability, and ejection stability can be attained with an ink containing resin emulsion in which a resin has urethane bonds by defining a primary particle diameter and DBP oil absorption of a carbon black.
• the aforementioned polyurethane resin tends to aggregate with influence of an organic solvent contained in an inkjet recording ink, and there are some cases where image fixing ability, ink storage stability and ejection stability are lowered. There have not yet been provided resin emulsion which can attain completely desirable these properties. Especially, a polyurethane resin suitable for pigment inks containing relatively fine pigment having a particle diameter of approximately 100 nm, surfactant-contained dispersing pigment inks and acid carbon black pigment inks has not yet been provided.
• Patent Literature 15 proposes an ink containing fine polymer particles, a water insoluble or poor soluble colorant, a water soluble organic solvent and a fluorine-contained surfactant.
• a nozzle plate tends to be easily wet, and thus it is difficult ensure ejection stability.
• Patent Literature 16 proposes an ink containing a water soluble solvent, a colorant, water, and a polymer containing an alkyleneoxide unit, aromatic ring unit, and carboxyl unit at least in a single molecule, and discloses “liquid-repellent treatment for an area including and surrounding an ejection opening,” and “containing a silicone surfactant, fluorine surfactant, or the like” in the specification thereof.
• this literature does not disclose any specific types of the silicone surfactant, and it is difficult to ensure liquid repellency with the low surface tension ink containing a fluorine-contained surfactant with the structure of this proposal.
• Patent Literature 17 proposes an aqueous dispersion for inkjet recording containing a self-dispersing pigment, polymer particles and a compound having a polysiloxane skeleton, and an aqueous ink containing the aqueous dispersion.
• this ink has a surface tension of 25 mN/m to 50 mN/m, and thus it has not been intended to be as a low-surface-tension ink and no special treatment is not applied to a nozzle plate.
• Patent Literature 18 proposes to reduce a surface tension of an inkjet ink so as to increase wettablity of the ink to a recording medium, thereby improving an image quality, and also proposes to add a silicone resin to an ink-repellent layer of a nozzle plate placed in an inkjet nozzle.
• a silicone resin to an ink-repellent layer of a nozzle plate placed in an inkjet nozzle.
• Patent Literature 19 proposes an inkjet recording ink containing a carbon black, a dispersant, a urethane resin and water in which the urethane resin has a glass transition temperature of 50° C. to 150° C., and a particle diameter D50 of 5 nm to 20 nm.
• A a particle diameter D90 of particles present in dispersion containing the carbon black, the dispersant and water, before added with the resin emulsion
• B a particle diameter D90 of particles present in the inkjet recording ink
• the examples disclosed in Patent Literature 19 use color pigments, not a carbon black.
• An object of the present invention is to provide an inkjet recording ink which realizes both shelf-stability and image quality, and prevents to solidify and attach to an inkjet head having an ink-repellent layer formed by PTFE-Ni eutectoid plating, or a treatment with a fluororesin or a silicone resin.
• Another object of the present invention is to provide an ink cartridge, an image forming method and an image recorded matter, using such the inkjet recording ink.
• the means for solving the aforementioned problems are as follows.
• an inkjet recording ink which realizes both shelf-stability and image quality, and prevents to solidify and attach to an inkjet head having an ink-repellent layer formed by PTFE-Ni eutectoid plating, or a treatment with a fluororesin or a silicone resin, as well as an ink cartridge, an image forming method and an image recorded matter, using such the inkjet recording ink.
• the inkjet recording ink of the present invention contains a carbon black, a dispersant, resin emulsion and water.
• the resin contained in the resin emulsion is at least one selected from a urethane resin and styrene-acryl resin.
• the resin emulsion is formed so as to surround a carbon black particle as a protective colloid, and as a result, shelf stability of the ink, image quality and image resistance are improved compared to the conventional ink.
• the ink does not need to be added with a releasing agent unlike conventional inks, as the ink has an improved releasability. Therefore, the problem of wetting due to the additive is solved, and thus it is possible to carry out continuous printing with the ink of the present invention.
• these resins have superior effect for improving friction resistance of a print by forming a film on a paper, compared to other resins. These resins also have effect for preventing coloring components from penetrating into paper, and promoting the fixation to the paper, since the resins have characteristics such that they increases their viscosities and/or aggregate at the time when the ink is arrived at paper such as a recording medium with an impact.
• the urethane resin is particularly preferable as it can improve dispersion stability of a carbon black.
• an image quality and image resistance can be further improved, while maintaining the shelf stability of the ink, provided that a combination thereof is suitably selected.
• the urethane resin for use in the present invention will be more specifically described.
• the urethane resin means a polymer compound mainly composed of a polyurethane skeleton in which a main chain includes a urethane bond as a repeating unit.
• a water-dispersible urethane resin is particularly preferable.
• water-dispersible urethane resin polyurethane aqueous dispersion obtained by introducing a hydrophilic component, which is necessary to make the resin stably dispersed in water, into a main chain of polyurethane skeleton, or dispersing the resin in assistance with external emulsifier is commonly known.
• a self-dispersing (self-emulsifying) urethane resin in which a hydrophilic component is introduced into the main chain is preferable.
• the water-dispersible urethane resin may be of any state, such as colloidal dispersion, emulsion, suspension, and slurry.
• water-dispersible urethane resin examples include various water-dispersible urethane resin (e.g. ester urethane resin, ether urethane resin, carbonate urethane resin) formed by reacting a diisocyanate compound, diol compound, and acid-group-contained diol.
• the diol compound examples include polyether diol, polyester diol, and polycarbonate diol.
• the acid group contained in the acid-group-contained diol include a carboxylic acid group, and sulfonic acid group.
• anionic self-emulsifying ether urethane resin is particularly preferable as the water-dispersible urethane resin.
• the diisocyanate compound examples include: an aliphatic diisocyanate compound such as hexamethylene diisocyanate, and 2,2,4-trimethylhexamethylene diisocyanate; an alicyclic diisocyanate compound such as isophorone diisocyanate, hydrogenated xylene diisocyanate, 1,4-cyclohexane diisocyanate, and 4,4′-dicyclohexylmethane diisocyanate; an aromatic/aliphatic diisocyanate compound such as xylene diisocyanate, and tetramethylxylene diisocyanate; an aromatic diisocyanate compound such as toluylene diisocyanate, and phenylmethane diisocyanate; modified products of these diisocyanate compounds, such as modified product thereof containing carbodiimide, uretodion, or uretoimine.
• an aliphatic diisocyanate compound such as hexamethylene
• diol compound examples include: polyether diol such as polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol; polyester diol such as polyethylene adipate, polybutylene adipate, polyneopentyl adipate, poly-3-methylpentyl adipate, polyethylene/butylene adipate, and polyneopentyl/hexyl adipate; polylactone diol such as polycaprolactone diol; and polycarbonate diol.
• polyether diol such as polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol
• polyester diol such as polyethylene adipate, polybutylene adipate, polyneopentyl adipate, poly-3-methylpentyl adipate, polyethylene/butylene adipate, and polyn
• the polyether diol compound, polyester diol compound and polycarbonate diol compound are preferably, the polyether diol compound and polycarbonate diol compound are more preferable, and the polyether diol compound is yet more preferable. Since the polyether diol compound and polycarbonate diol compound are unlikely to change their properties by hydrolysis in water, leading desirable storage stability.
• acid-group-contained diol examples include dimethylol acetate, dimethylol butanoate, dimethylol propionate, and dimethylol butyrate. Among them, dimethylol butanoate is particularly preferable.
• the synthesis method of the urethane resin is selected from any known methods in the art without any limitation.
• Examples of such synthesis method include: a solution method in which a prepolymer containing isocyanate terminals is synthesized in a solvent of a low boiling point that does not react with an isocyanate group, an hydrophilic group(s) is (are) introduced into the prepolymer using diamine, polyol or the like, it is then diluted with water so as to cause a phase transition, the solvent is removed therefore so as to obtain polyurethane dispersion; a prepolymer method in which isocyanate-terminated prepolymer to which a hydrophilic group(s) is (are) introduced is synthesized, the prepolymer is dispersed in water, and reacted with amine so as to elongate the chain, a hot-melt method, a method in which a urethane prepolymer is reacted in an emulsifier-contained aqueous
• a polyhydroxy compound of low molecular weight may be used.
• the low-molecular weight polyhydroxy compound include those listed above as materials for the polyester diol, such as glycol and alkylene oxide low molar adducts thereof, trivalent alcohol such as glycerin, trimethylol ethane, and trimethylol propane, and alkylene oxide low molar adducts thereof.
• the generally known method for synthesizing the water-dispersible urethane resin is such that a urethane prepolymer formed in an organic solvent phase is phrase transitioned so as to emulsify, and is then chain-elongated in an aqueous phase.
• a chain elongation agent for this polyamines such as diamine are generally known.
• the urethane prepolymer is water-extended or di- or triamine-extended.
• the polyamine for use in the amine extension as a chain elongation agent is generally diamine or triamine. Specific examples thereof include hexamethylene diamine, isophorone diamine, hydrazine, and piperazine.
• urethane resin formed by using polyamine tends to adversely affect to storage stability of a recording liquid. This is probably because the urethane resin obtained by amine extension (i.e. the urethane resin containing a polyurethane urea portion) is likely to cause hydrolysis, and polyamines yielded as a byproduct of the hydrolysis functions as an aggregating agent in a carbon black-dispersed recording liquid, as a result such urethane resin has dual adverse effects to the resulting recording liquid.
• the urethane resin can be used in the form of an alkali metal salt such as Li, Na and K, or organic amine salt such as ammonia, dimethyl amine, and (mono-, di-, tri-)ethanol amine. These can be obtained by further neutralizing the urethane resin formed by the aforementioned method.
• an alkali metal salt such as Li, Na and K
• organic amine salt such as ammonia, dimethyl amine, and (mono-, di-, tri-)ethanol amine.
• the base used at the time of neutralization is suitably selected depending on a counter ion of the intended salt.
• examples thereof include: alkyl amine such as butyl amine and triethyl amine; alkanol amine such as monoethanol amine, diethanol amine, and triethanol amine; and inorganic base such as morpholine, ammonia, and sodium hydroxide.
• the styrene-acryl resin can be prepared in an aqueous medium in accordance with a free-radical emulsifying polymerization method known in the art, by using one kind of a monomer so as to form a homopolymer or using two or more kinds of monomers so as to form a copolymer.
• a polymer containing a monomer capable of forming a water-insoluble homopolymer is preferable as well as a copolymer of such monomer.
• the polymer can include a monomer capable of forming a water-insoluble homopolymer, provided that the polymer composition is sufficiently water-insoluble on the whole enough to form latex.
• polymers can be prepared by emulsion polymerization, solution polymerization, suspension polymerization, dispersion polymerization, ionic polymerization (e.g. cationic and anionic), atomic transfer radical polymerization and other polymerization methods known in the technical field of polymerization.
• ionic polymerization e.g. cationic and anionic
• atomic transfer radical polymerization e.g. atomic transfer radical polymerization
• the polymer include a styrene-acryl resin prepared by a free radical polymerization of a vinyl monomer in aqueous emulsion.
• the polymer latex is preferable a homopolymer, copolymer or cross-linked polymer each containing a hydrophobic unsaturated ethylene monomer(s) capable of forming a water-insoluble homopolymer.
• a copolymer of monomers containing a hydrophilic unsaturated ethylene monomer(s) is preferable, provided that the polymer composition is sufficiently water-insoluble on the whole enough to form a latex.
• styrene-acryl resins can be prepared by emulsion polymerization, dispersion polymerization, suspension polymerization, pulverization or solution/bulk polymerization.
• the details of the methods and stabilizer for use can be found in “Emulsion Polymerization and Emulsion Polymer,” P. A. Lovell, and M. S. El-Aasser, John Wiley & Sons Ltd., England, 1977), and are incorporated herein by the reference.
• Examples of the commercially available resin emulsion include: J-450, J-734, J-7600, J-352, J-390, J-7100, J-741, J-74J, J-511, J-840, J-775, HRC-1645, HPD-71, PDX-6102B, and JDX-5050 (styrene-acryl resin emulsion, manufactured by BASF JAPAN LTD.); UC-3900 (styrene-acryl resin emulsion, manufactured by Toagosei Co., Ltd.); SF460, SF460S, SF420, SF110, SF300, and SF361 (polyurethane resin emulsion, manufactured by Nippon Unicar Company Limited); and W-6020, W-5025, W-5661, and W-6010 (polyurethane resin emulsion, manufactured by Mitsui Chemicals, Inc.).
• the inkjet recording ink of the present invention satisfies the relationship of 20 ⁇ B ⁇ A ⁇ 50, and preferably satisfies the relationship of 20 ⁇ B ⁇ A ⁇ 30, where A (nm) is a particle diameter D90 of particles contained in dispersion containing a carbon black, dispersant and water before added with the resin emulsion, and B (nm) is a particle diameter D90 of particles contained in the inkjet recording ink.
• the average particle diameter D50 of the resin emulsion is preferably 5 nm to 20 nm.
• the resin emulsion is easily attached to the surroundings of the carbon black, and the vale of B ⁇ A is equivalent to a thickness of a protective layer (i.e. a simulated capsule layer) of the resin emulsion.
• the average particle diameter D50 of the resin emulsion is more preferably 5 nm to 10 nm.
• the dispersion stability or ejection performance of the ink may be lowered.
• the value of B ⁇ A is less than 20 nm, the resin emulsion does not sufficiently attach to the carbon black, and thus dispersion stability of the ink may be lowered depending on the formulation of the ink such that the amount of diol solvent or a solvent is large.
• the inkjet recording ink of the present invention satisfies the relationship of 0 nm ⁇ C ⁇ B ⁇ 15 nm, where B (nm) is the particle diameter as mentioned above, and C is a particle diameter D90 of particles contained in the ink after being stored at 70° C. for 24 hours.
• the value of C ⁇ B being more than 15 nm when the ink is stored at a high temperature means that the dispersion becomes unstable during storage for a period of time.
• the dried film of the resin emulsion has a glass transition temperature Tg of preferably 50° C. to 150° C., more preferably 75° C. to 125° C.
• Tg glass transition temperature
• the glass transition temperature of the dried film of the resin emulsion is in the range of 50° C. to 150° C.
• the bonding between the fibers of the paper becomes strong.
• the dried film is relatively hard, and thus it does not peel even when sticks to a head. Accordingly, such the dried film is suitable for the present invention.
• the glass transition temperature thereof is less than 50° C.
• the resin particles are easily deformed.
• the glass transition temperature is more than 150° C., the resin emulsion cannot form a film easily.
• the glass transition temperature of the dried film of the resin emulsion can be determined by a differential scanning chromatography (DSC), or thermomechanical analysis (TMA).
• DSC differential scanning chromatography
• TMA thermomechanical analysis
• the average particle diameter D50 of particles contained in the inkjet recording ink is preferably 100 nm to 200 nm, more preferably 100 nm to 150 nm.
• the average particle diameter D50 is less than 100 nm, carbon black may penetrate into an inner portion of normal paper, and as a result prints of high optical density may not be obtained.
• the average particle diameter D50 is more than 200 nm, the ejection performance may be lowered.
• the particle diameters D50, D90 used in the present invention can be measured by any conventional method. For example, they can be measured by using a particle size analyzer UPA150, manufactured by Nikkiso Co., Ltd.
• the particle diameters D50, D90 can be controlled by adjusting peripheral speed of a rotational portion of a disperser, duration for dispersing, flow rate of dispersion, and a temperature of dispersion at the time when a carbon black is dispersed by means of a disperser.
• a media mill for use in the present invention can be suitably selected depending on the intended purpose without any restriction.
• examples thereof include TORUSMILL manufactured by VMA-GETZMANN GMBH, Starmill manufactured by Ashizawa Finetech Ltd., Biscomill manufactured by AIMEX Co. Ltd., DYNO-MILL manufactured by Shinmaru Enterprises Corporation, DIAMOND FINE MILL manufactured by Mitsubishi Heavy Industries, Ltd., Apex Mega manufactured by Kotobushi Engineering & Manufacturing Co., Ltd., PICO GRAIN MILL manufactured by Asada Iron Works Co., Ltd., OB BEADS MILL manufactured by Eurotec Ltd., and SC MILL manufactured by Mitsui Mining Company Limited.
• a media-less mill for use in the present invention is suitably selected depending on the intended purpose without any restriction, and examples thereof include T.K. FILMICS manufactured by PRIMIX Corporation, Altemizer manufactured by Sugino Machine Limited, CLEAR SS5 and CLEARMIX W-MOTION both manufactured by M Technique Co., Ltd., CAVITRON manufactured by Eurotec Ltd., IKA DR2000 manufactured by Shinmaru Enterprises Corporation.
• dispersion may be performed by the aforementioned media-less mill before dispersion by the media mill. This is preferable, as dispersibility of coarse particles of 1 ⁇ m or more is especially improved, and a standard deviation in a particle size distribution of carbon black particles at the time of later dispersion by a beads mill becomes small.
• use of the aforementioned media-less mill after dispersion by the media mill contributes to reduce the surface roughness of the carbon black, and to improve dispersion stability.
• the amount of the resin emulsion contained in the inkjet recording ink of the present invention is preferably 0.1% by mass to 10% by mass, more preferably 0.2% by mass to 5% by mass on resin solid basis.
• the amount is less than 0.1% by mass, the resin covers carbon black when the ink is landed on a recording medium with impact, the amount of the resin forming a protective colloid becomes insufficient, and thus abrasion resistance may become lower.
• the amount thereof is more than 10% by mass, the viscosity of the ink is too high to smoothly perform printing in the inkjet system.
• the acid value of free acid contained in the urethane resin for use in the present invention is preferably 50 to 100, more preferably 55 to 95 in view of further enhanced storage stability and ejection stability of recording liquid.
• the acid value When the acid value is less than 50, water solubility may not be exhibited. When the acid value is more than 100, problems occur such that abrasion resistance and water resistance of the coated film may be lowered, viscosity of the ink becomes excessively high, and ejection performance is lowered.
• the weight average molecular weight of the urethane resin is preferably 10,000 to 30,000 in view of ejection stability. When the weight average molecular weight is more than 30,000, the viscosity is increased and as a result, ink may not be ejected easily. When the weight average molecular weight is less than 10,000, water solubility of the urethane resin becomes high, effect for imparting gloss is reduced, and liquid stability is also lowered.
• the acid value of free acid contained in the styrene-acryl resin is preferably 100 to 200, more preferably 125 to 175.
• the weight average molecular weight of the styrene-acryl resin is preferably 10,000 to 30,000. The reasons for the preferences of the ranges are the same as in the case of the urethane resin.
• the dispersant for use in the present invention is preferably a condensation product of sodium naphthalenesulfonate and formaldehyde, i.e. sodium naphthalenesulfonate-formalin condensate.
• the dispersant is not particularly limited as long as it is equivalent to the condensation product, but those having a total amount of dimer, trimer, tetramer of naphthalene sulfonate of 20% by mass to 80% by mass with respect to the total amount of the condensation product are preferable.
• the mixing ratio of the carbon black to the dispersant i.e. the carbon black/the dispersant, is preferably 1/0.01 to 1/2, more preferably 1/0.05 to 1/0.5 on mass basis.
• the ratio of the dispersant is less than 0.01, the function of the dispersant is hard to be exhibited, storage stability of aqueous carbon black dispersion and ink is lowered, and as a result, clog of the nozzle may be likely occurred.
• the ratio of the dispersant is more than 2, the viscosity of the aqueous carbon black dispersion and ink is too high to smoothly perform printing in the inkjet system.
• the carbon black for use in the present invention preferably has DBP oil absorption of 300 g/100 g to 750 g/100 g, more preferably 350 g/100 g to 700 g/100 g.
• the carbon black of high structure can attain high optical density (OD), it is preferred that the carbon black have DBP oil absorption of the aforementioned range.
• the inkjet recording ink of the present invention preferably contains a wetting agent as one of the components, and the wetting agent preferably has a boiling point of 180° C. or more.
• the wetting agent When the wetting agent is contained in an aqueous carbon black ink, water retention and wettability of the ink composition can be maintained. As a result, even after storing the aqueous carbon black ink for long period of time, aggregation of a colorant or increase in the viscosity of ink is not seen, and excellent storage stability can be achieved.
• such an inkjet recording ink that can maintain the fluidity of the dried product thereof when the ink is left open at a tip of a nozzle of an inkjet printer can be provided. Furthermore, during printing or at the time of restating after interruption of printing, the nozzle is not clogged, and high ejection stability can be attained.
• wetting agent examples include: polyhydric alcohols such as ethylene glycol, diethylene glycol, 1,3-butyl glycol, 3-methyl-1,3-butyl glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,5-pentan diol, 1,6-hexane diol, glycerin, 1,2,6-hexane triol, 2-ethyl-1,3-hexane diol, 1,2,4-butane triol, 1,2,3-butane triol, and petriol; polyhydric alcohol alkyl ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl
• wetting agents may be used independently, or in combination.
• wetting agents those containing 1,3-butyl glycol, 3-methyl-1,3-butyl glycol, diethylene glycol, triethylene glycol and/or glycerin are preferable.
• wetting agents excellent effects can be attained in terms of the prevention of clog due to the dried ink, i.e. jet failure due to evaporation of water, and improvement of chroma of resulting images.
• the inkjet recording ink of the present invention may contain a penetrating agent as one of the components.
• a penetrating agent examples include polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene glycol ester, polyoxyethylene/polyoxypropylene decyl ether, or nonionic surfactants such as acetylene surfactant, silicone surfactant, and fluorosurfactant.
• fluorosurfactant examples include perfluoroalkyl sulfonate, perfluoroalkyl carbonate, perfluoroalkyl phosphate, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl betaine, and a perfluoroalkyl amine oxide compound.
• the compounds represented by following formulae are preferable in view of the reliability of the compounds.
• n represents an integer of 0 to 40.
• Rf represents a fluorine-containing group, e.g. CF 3 , and CF 2 CF 3 , m represents an integer of 6 to 25, n represents an integer of 1 to 4, and p represents an integer of 1 to 4.
• the fluorosurfactant may be arbitrarily synthesized for use, or selected from commercially available products.
• Examples of the commercially available products include: S-144, and S-145, both manufactured by Asahi Glass Co., Ltd.; FC-170C, FC-430, and Fluorad-FC4430, all manufactured by Sumitomo 3M Limited; FSO, FSO-100, FSN, FSN-100, and FS-300, all manufactured by Du Pont Kabushiki Kaisha; and FT-250, and FT-251, both manufactured by Neos Company Limited.
• FSO, FSO-100, FSN, FSN-100, and FS-300 of Du Pont Kabushiki Kaisha are preferable as they can provide desirable a printing quality and shelf stability.
• fluorosurfactants may be used independently, or in combination.
• the amount of the fluorosurfactant contained in the inkjet recording ink is preferably 0.1% by mass to 10% by mass, more preferably 0.1% by mass to 5% by mass.
• the amount of the fluorosurfactant is less than 0.1% by mass, the penetration of the ink is not significantly improved.
• the amount thereof is more than 10% by mass, the viscosity increases and aggregation occurs when the ink is stored at a high temperature, and thus the reliability of the ink is lowered.
• examples of the commercially available products of the nonionic surfactant other than the fluorosurfactant include BT series manufactured by Nikko Chemicals Co., Ltd., Nonipol series manufactured by Sanyo Chemical Industries, Ltd., D-series and P-series both manufactured by Takemoto Oil & Fat Co., Ltd., Surfinol series manufactured by Air Products Japan, Inc., OLFINE series manufactured by Nisshin Chemical Industry Co., Ltd., and EMALEX DAPE series manufactured by Nihon-Emulsion Co., Ltd.
• substances contained in the inkjet recording ink of the present invention can be suitably selected depending on the necessity without any restriction.
• examples thereof include a defoaming agent, preservative and fungicide, pH adjusting agent, antirust agent, ultraviolet absorber, oxygen absorber, and photostabilizer.
• the defoaming agent is suitably selected depending on the intended purpose without any restriction.
• Preferable examples thereof include a silicone defoaming agent, polyether defoaming agent, and fatty acid ester defoaming agent. These may be used independently, or in combination.
• the silicone defoaming agent is preferable as it excels in the defoaming effect.
• preservative and fungicide examples include 1,2-benzisothiazoline-3-on, sodium dehydroacetate, sodium sorbate, sodium-2-pyridinethiol-1-oxide, sodium benzoate, and sodium pentachlorophenolate.
• any arbitrary selected compound can be used depending on the intended purpose provided that it does not adversely affect the ink to be formulated and can control the pH value of the ink to be 7 or more.
• examples thereof include: amines such as diethanol amine, and triethanol amine; alkali-metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; ammonium hydroxide; quaternary ammonium hydroxide; quaternary phosphonium hydroxide; and alkali-metal carbonates such as lithium carbonate, sodium carbonate and potassium carbonate.
• antirust agent examples include acid sulfite, sodium thiosulfate, ammonium thioglycolate, diisopropyl ammonium nitrite, pentaerythritol tetranitrate, and dicyclohexyl ammonium nitrite.
• antioxidants examples include phenol antioxidants including hindered phenol antioxidants, amine antioxidants, sulfur antioxidants, and phosphorous antioxidants.
• the physical properties of the inkjet recording ink of the present invention are suitably selected and adjusted depending on the intended purpose without any restriction.
• the viscosity, surface tension and pH are preferable in the ranges stated below.
• the viscosity is preferably 5 mPa ⁇ s to 20 mPa ⁇ s, more preferably 6 mPa ⁇ s to 15 mPa ⁇ s at 25° C. When the viscosity is more than 20 mPa ⁇ s, it may be difficult to ensure the ejection stability of the ink.
• the surface tension is preferably 20 mN/m to 40 mN/m at 25° C.
• the surface tension is less than 20 mN/m, there are cases where bleeding is significantly appeared on a recording medium, and stable jetting cannot be attained.
• the surface tension is more than 40 mN/m, the penetration of the ink to a recording medium becomes insufficient, and thus the time required for drying the ink may be prolonged.
• the pH value is preferably 7 to 10.
• the inkjet recording ink of the present is preferably subjected to vacuum or pressure filtration with a metal filter or membrane filter, or centrifugal filtration so as to remove coarse particles and foreign matters (e.g. dusts).
• An ink cartridge housing the inkjet recording ink of the present invention may be prepared.
• Such ink cartridge can be placed in an inkjet device, and the inkjet device can provide image formed matter by ejecting the ink corresponding to a recording signal, and forming an image on a recording medium.
• an inkjet system printer i.e. an inkjet printer, having a continuous jetting recording head or an on-demand recording head
• the on-demand system include a piezo system, thermal inkjet system and electrostatic system.
• a nozzle plate is formed from a metal material. For example, it is formed of a Ni-plating film by an electroplating.
• the nozzle plate has a plurality of nozzles that are fine ejecting openings for jetting ink droplets.
• the interior configuration, i.e. inner shape, of the nozzle may be in the shape of horn (including a substantially cylinder or truncated cone).
• the aperture of the nozzle is about 20 ⁇ m to 35 ⁇ m based on the diameter at the ink droplet outlet side.
• the pitch of each nozzle array is 150 dpi.
• an ink-repellent layer is disposed on the ink ejecting side (nozzle surface side) of the nozzle plate.
• the water-repellent treatment is preferably at least one of PTFE-Ni eutectoid plating, fluororesin treatment and silicone resin treatment. Among them, the most preferably is that the ink-repellent layer containing a silicone resin is disposed on a surface of the nozzle plate.
• the silicone resin is a resin having a siloxane bond consisting of Si and O as a basic skeleton, and is commercially available in various forms such as oil and elastomer. Other than ink repellency that is important in the present invention, the silicone resin has various characteristics such as heat resistance, releasing property, defoaming property, and adhesiveness.
• the silicone resin has various types such as cold setting, heat setting, and ultraviolet setting, and the type thereof can be selected depending on a preparing method or intended use.
• the method for forming the ink-repellent layer containing the silicone resin on the nozzle surface is, for example, a method in which a silicone resin material in the form of liquid is vacuum-deposited, a method in which the ink-repellent layer is formed by plasma-polymerizing silicone oil, a method in which the ink-repellent layer is formed by coating such as spin coating, dip coating and spray coating, an electrodeposition method, or the like.
• the ink-repellent layer is formed by a method other than the electrodeposition method
• the ink-repellent layer is formed while nozzle openings and a back surface of a nozzle plate are masked with a photoresist or water-soluble resin, and then the resist is peeled and removed so that the ink-repellent layer containing the silicone resin is only formed on the surface of the nozzle plate.
• the selection of a peeling liquid (a developer) for use needs to be carefully considered as the releasing liquid of strong alkali may damage the ink-repellent layer.
• the thickness of the ink-repellent layer containing the silicone resin is preferably 0.1 ⁇ m to 5.0 ⁇ m, more preferably 0.1 ⁇ m to 1.0 ⁇ m. When the thickness thereof is less than 0.1 ⁇ m, resistance to wiping may be lowered, and ink repellency may be lowered after a long period of use. When the thickness thereof is more than 5.0 ⁇ m, the ink-repellent layer has a thickness of more than necessary, and thus the production cost may be increased.
• the surface roughness Ra of the ink-repellent layer is preferably 0.2 ⁇ m or less. By having the surface roughness of 0.2 ⁇ m or less, the remaining ink from wiping can be reduced.
• an ultraviolet setting liquid silicone resin or elastomer is used as the silicone water-repellent material, such resin or elastomer is applied on a surface of a base, and then exposed to an ultraviolet ray for curing so as to form an ink-repellent film.
• the viscosity of the silicone water-repellent material is preferably 1,000 cp (centipoise) or less.
• the critical surface tension of the ink-repellent layer is preferably 5 mN/m to 40 mN/m, more preferably 5 mN/m to 30 mN/m.
• the critical surface tension thereof is more than 30 mN/m, there are cases where nozzle plate is excessively wetted with the ink during a long period of use, and the direction for the ejection of the ink may be curved without intension or failures in atomizing of the ink may be cause as printing is repeated.
• the critical surface tension thereof is more than 40 mN/m, there are cases where nozzle plate is excessively wetted with the ink from the initial stage of printing, and the direction for the ejection of the ink may be curved without intension or failures in atomizing of the ink may be cause as printing is repeated.
• the critical surface tension can also be determined by other methods such as a method of Fowkes, method of Owens and Wendt, and method of Van Oss.
• the preparation method of the ink cartridge, formation method of the inkjet device and image forming method can be arbitrary selected from techniques known in the art, such as the technique disclosed in JP-A No. 2000-198958.
• a recording medium for use with the inkjet recording ink of the present invention in the inkjet recording system can be paper which shows absorption to the ink composition, or a medium which shows substantially no absorption to the ink composition.
• paper is particularly preferable in view of the cost efficiency and obtainable natural image.
• ink Nos. 1-27 are corresponded to the inks used in Examples 1 to 27, respectively, and ink Nos. 1′-2′ are corresponded to the inks used in Comparative Examples 1 to 2.
• ink No. 3 was used in Example 28, which was the same ink used in Example 3.
• the particle diameter D90 (B) of particles contained in each ink was approximately the same as the average particle diameter D50 of the particles in the ink plus 100 nm.
• carbon black dispersion was prepared in the following manner.
• the mixture of the followings was premixed so as to obtain mixed slurry.
• the slurry was circulated and dispersed by means of a disk media mill (UAM, manufactured by Kotobuki Industries Co., Ltd.) in which zirconia beads of 0.015 mm were used at the filling rate of 70%, at the peripheral speed of 6 m/s, and liquid temperature of 10° C. for 10 minutes, and then subjected to centrifugal separation by means of a centrifugal separator (Model-7700, manufactured by KUBOTA Corporation) so as to separate coarse particles to thereby obtain carbon black dispersion.
• UAM disk media mill
• a centrifugal separator Model-7700, manufactured by KUBOTA Corporation
• the acid value of the polyurethane resin or styrene-acryl resin was altered by controlling the amount of the functional group present on the surface of the polyurethane resin or styrene-acryl resin, and molecular weight of the polyurethane resin or styrene-acryl resin was altered by selecting the polymerization method of monomers.
• Tg represents a glass transition temperature
• D50 represents a particle diameter D50
• Mw represents a weight average molecular weight
• Tg represents a glass transition temperature
• D50 represents a particle diameter D50
• Mw represents a weight average molecular weight
• a carbon black ink was prepared by using the aforementioned carbon black dispersant according to the ink formula below, and after dispersing for 30 minutes, filtered with a membrane filter having a pore diameter of 0.8 ⁇ m, followed by vacuum deairing, to thereby obtain carbon black ink of Example (No. 1).
• the carbon black inks of Examples (Nos. 2-28), and Comparative Examples (Nos. 1-2) were obtained in the same manner.
• the thus obtained carbon black ink was filled in an ink pack for an inkjet printer (IPSiO GX 3000, manufactured by Ricoh Company Limited) so as to prepare an ink cartridge.
• IPSiO GX 3000 manufactured by Ricoh Company Limited
• a silicone resin (SR2411, manufactured by Dow Corning Toray Co., Ltd.) was applied by a dispenser so as to form a silicone layer.
• nozzle openings and back surface of the nozzle plate were masked with a water-soluble resin, and the mask was peeled and removed after the formation of the silicone layer.
• the silicone layer was then left to stand at a room temperature for 2 days so as to cure the silicone resin, to thereby obtain an ink-repellent layer having a thickness of 1.2 ⁇ m.
• the thus obtained ink-repellent layer had a surface roughness (Ra) of 0.18 ⁇ m, and critical surface tension of 21.6 mN/m.
• a thickness of the ink -repellent layer was measured by a spectrometric film thickness measurement system (LAMBDA ACE VM-8000J, manufactured by Dainippon Screen Mfg. Co., Ltd.). Moreover, the surface roughness of the ink-repellent layer was measured by a stylus surface profiler (Dektak 3-ST, manufactured by Veeco Instruments Inc.). The critical surface tension of the ink-repellent layer was measured in accordance with a method proposed by Zisman.
• An ink-repellent layer having a thickness of 1.0 ⁇ m was formed in the same manner as in Preparation Example 1, provided that the silicone resin used in Preparation Example 1 was replaced with a silicone resin (KBM 7803, manufactured by Shin-Etsu Chemical Co., Ltd.).
• the surface roughness (Ra) and critical surface tension of the thus obtained ink-repellent layer were measured in the same manner as in Preparation Example 1, and were 0.2 ⁇ m and 16.9 mN/m, respectively.
• a nozzle plate 3 was formed in the same manner as in Preparation Example 1, provided that an ink-repellent layer was formed on the Ni electroformed nozzle surface by PTFE-Ni eutectoid plating, instead of the ink-repellent layer formed of the silicone resin of Preparation Example 1.
• the surface roughness (Ra) and critical surface tension of the thus obtained ink-repellent layer were measured in the same manner as in Preparation Example 1, and were 0.25 ⁇ m and 25.0mN/m, respectively.
• a nozzle plate 4 was formed in the same manner as in Preparation Example 1, provided that an ink-repellent layer was formed on the Ni electroformed nozzle surface by treating with a fluororesin, instead of the ink-repellent layer formed of the silicone resin of Preparation Example 1.
• the surface roughness (Ra) and critical surface tension were measured in the same manner as in Preparation Example 1, and were 0.30 ⁇ m and 22.0 mN/m, respectively.
• a nozzle plate 5 was formed in the same manner as in Preparation Example 1, provided that the ink-repellent layer formed of the silicone resin was not formed on the Ni electroformed nozzle surface.
• nozzle plates 1 to 5 were each disposed in an inkjet printer (IPSiO GX 3000, manufactured by Ricoh Company Limited), and each inkjet printer printed on PPC paper (XEROX 4024, manufactured by Fuji Xerox Co., Ltd.).
• IPSiO GX 3000 manufactured by Ricoh Company Limited
• XEROX 4024 manufactured by Fuji Xerox Co., Ltd.
• the ejection stability, image density and shelf-stability of the ink were evaluated by the following manner.
• the printer was placed in a thermohygrostat which was set at the temperature of 32° C. and humidity of 30% RH, and continuously printed the print pattern chart described below on 20 pieces of the paper, and then rested for 20 minutes without printing. This procedure was repeated for 50 times, and after printing on 1,000 pieces of the paper in total, the nozzle plate was observed under a microscope to confirm whether or not any ink solid was attached to the nozzle plate.
• the used print pattern was a chart in which each color occupied 5% of the total area of the paper, and the printing was performed using each ink at 100% duty based on the print pattern.
• the recording density was set at 300 dpi, and the system for use was a one-pass printing system.
• the evaluation criteria were as follows.
• the image density of the solid image portion in the image sample was measured by means of X-Rite densitometer.
• the evaluation criteria were as follows.
• each ink was placed in a polyethylene container, and the container was sealed. In this condition, the ink was stored at 70° C. for 3 weeks. After the storage, a particle diameter, surface tension and viscosity of the ink were measured, and compared to the initial physical properties of the ink. The rates of the changes (%) were evaluated with reference to the following evaluation criteria.
• the inkjet recording ink of the present invention can realize both shelf-stability and image quality, and prevents to solidify and attach to an inkjet head having an ink-repellent layer formed by PTFE-Ni eutectoid plating, or a treatment with a fluororesin or a silicone resin.
• the ink cartridge and image forming method using the inkjet recording ink of the present invention can form high quality images, and as a result, an image recorded matter of high quality image can be obtained.

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• Ink Jet Recording Methods And Recording Media Thereof (AREA)
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• 2008
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